Plutonium-239

Isotope of plutonium

Plutonium-239 (239Pu or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three isotopes that have been demonstrated to be usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233.

From Wikipedia, under CC BY-SA. More on occurri.